High capacity combustion heater



Sept. 2 1958 G. J. FAIRBANKS 2,350,004 HIGH CAPACITY COMBUSTION HEATER File d Dec. 21. 1954 s Sheets-Sheet 1 aw 1 1g;

Sept. 2; 1958 r G. J. FAIRBANKS 1' 2,850,004 men CAPACITY COMBUSTION HEATER Sept. 2, 1958 G. JI FAIRBANKS 7 0, 0

HIGH CAPACITY COMBUSTION HEATER Filed D9C.-2l, 1954 3 Sheets-Shee t 5 v 51 $1 N P I II I I II I y g I 'I- N I =IL N II I H I II v a I1 III Q I I I Q 0 I I Q- I I I t\ I I I I I I I Q I I l I I I I I I l United States Patent HIGH CAPACITY COMBUSTION HEATER Gordon J. Fairbanks, Indianapolis, Ind., assignor to Stewart-Warner Corporation, Chicago, 111., a corporation of Virginia Application December 21, 1954, Serial No. 476,751

2 Claims. (Cl. 126-116) The present invention relates to high capacity liquid fuel combustion heaters. It is highly desirable that heaters, such, for example, as are used for the heating of automotive vehicles, be of high capacity (e. g. 30,000 to 60,000 B. t. u. per hour) and that they be of minimum size and weight. To obtain these objectives in the heater of the present invention, the air which supports combustion is caused to flow at high velocity through a relatively small combustion space. Ordinarily this would tend to cause inefficiency due to poor mixing and incomplete or delayed burning of the liquid fuel in the high velocity stream of combustion air. However, in the heater of the present invention means are provided greatly to improve the efficiency of combustion and heat transfer, despite the high velocity at which the combustion air flows through the heater.

One object of the invention is to provide an improved heater in which the combustion eificiency is increased more completely to utilize the heating value of the fuel consumed and increase the heat output capacity of the heater, while at the same time preserving or decreasing the ratio of the size and weight of the heater to its heat output capacity.

A more specific object is to provide an improved heater of the above character in which the combustion eificiency is increased by improved preheating of the combustion air and a more thorough mixing of the fuel and air.

Another object is to provide a heater of the character recited in the previous object, in which premature exhausting of the burning fuel mixture from the combustion space is avoided and the hot combustion gases are evenly distributed to the heat transfer structure.

An additional object is to provide an improved heater of the character recitedin the above objects which has a simple construction well adapted for economical manufacture.

Other objects and advantages will become apparent from the following description of the form of the invention illustrated in the drawings, in which:

Figure 1 is a longitudinal sectional view of the basic structure of a combustion heater embodying the inventron;

Fig. 2 is a sectional view taken along line 22 of Fig. 1;

Fig. 3 is a fragmentary vertical sectional view taken generally along the line 3-3 of Fig. 2;

Fig. 4 is a vertical sectional view taken along the line 44 of Fig. 1;

Fig. 5 is a horizontal sectional view taken along the line 5'----5 of Fig. 4; and

Fig. 6 is a fragmentary sectional view taken generally along the broken line 66 of Fig. 4.

The heater structure forming the illustrated embodi- -ment of the invention comprises an elongated heat ex- Patented Sept. 2, 1958 ICC the specific heat exchanger shown reference may be made to the application of Frank A. Ryder, Combustion Heater Sheet Metal Heat Exchanger, Serial No. 388,096, filed October 26, 1953.

In general, the heat exchanger 10 shown comprises a folded sheet metal envelope 14 of generally C-shaped transverse configuration extending longitudinally through a cylindrical outer shell 16 in radially spaced relation to the shell. The circumferential end edges of the shell 16 are offset radially inward and welded or otherwise secured to the adjacent marginal edges of the outer fold 18 of the envelope 14. The inner fold 20 of the envelope is radially spaced from the outer fold to form open ended longitudinal passages 22 through the heat exchanger for air to be heated. Heat transfer fin members 24 secured to the inner envelope fold 20 extend radially into the passages 22.

Two vertical header plates 26 and 28 are fixed in opposite ends of the heat exchanger 10, the peripheral edges of the headers being secured to the adjacent marginal edges of the inner envelope fold 20 and to end segments 30 of the shell 16, Fig. 2, between the extremities of the upwardly open envelope. The headers 26, 28 together with the envelope 14, define the previously mentioned combustion chamber 12, which opens upwardly through a longitudinal passageway 32, formed by the horizontally spaced upper extremities of the envelope, Figs. 1 and 4. The passageway 32 connects with radially thin arcuate passages 34 extending circumferentially around the envelope 14 to an exhaust connection 36 in lower medial portion of the shell 16.

To provide additional support to the envelope 14, and to increase the effective size of the lower portion of the combustion gas passageway 34 which connects with the outlet 36, the lower side of the outer envelope fold 18 is flattened upwardly at 38 to be contiguous with the inner fold 20, Figs. 1 and 2.

Air to support combustion is supplied to the heater from conventional air scoop or blower structure (not shown) connected with a large conduit 42 extending to the left end of the heat exchanger 10, Fig. 1, and connected by an annular coupling member 44 to the periphery of the header 26. A fuel line 46 extends downwardly through the conduit 42 to a fuel supply fitting 48 of conventional construction which protrudes through an opening 50 in the lower central portion of the header 26. An electric supply line 52 extends downwardly through a conduit 54 to the fitting 48 to energize a conventional electrical igniter (not shown) in the fitting.

The fuel supply fitting 48 discharges fuel through the header opening 50 into the lower portion of a truncated burner cone 56 having a small apex angle. The large end of the cone 56 is mounted for support between the periphery of the header 26 and the contiguous portions of the envelope 14 and the shell 16. The shell 56 extends for a substantial distance 7 into the combustion chamber 12 and is rolled inwardly at its free end 53 to a somewhat restricted diameter.

A small opening 59 formed through the bottom of the inner fold 20 and the outer told 18 where they are brought together at 38 permits any liquid which might otherwise collect within the combustion chamber 12 to drain to the exhaust fitting at 36. This opening is preferably located near the inlet end of the heater beneath the burner cone 56 so that the cone acts to baffle the opening to prevent an excessive gas flow therethrough. The two thicknesses of metal should be welded together around this opening to prevent leakage of combustion gases or liquid into the ventilating air stream.

Extremely efficient combustion is obtained through an improved mixing and burning of the fuel in a high velocity vortex of thoroughly preheated air, provision being made to avoid premature discharging of the burning gas by centrifugal force through the longitudinal combustion chamber outlet.

Combustion air supplied under pressure through the conduit 42 flows through an opening 60 in the central right hand portion of the header 26 (as viewed from the left in Fig. 1, see Fig. 2) into the closed end of a semicircular duct 62 attached to the inner face of the header 26. From the opening 60, the duct 62 extends circumferentially over and around the center of the header 26 in radially spaced relation to the burner cone 56 to a downwardly open end 64, Figs. 3 to 6.

Structurally the duct 62 is formed from two arcuate sheet metal members 68, 70, U-shaped in transverse section, attached to the inner face of the header 26 in end to end overlapping relation to each other. The width of the duct 62 in transverse section preferably is somewhat greater along the axis of the burner cone 56 than in a radial direction from the center of cone, thus providing extensive heat transfer area to the air supplied through the duct.

After turning approximately 180 around the axis of the burner cone 56 in passing through the duct 62, the air is directed downwardly from the outlet 64 of the duct with a high circular velocity which sweeps circumferentially over the lower inner surface of the cone 56 to pick up the fuel supplied from the fixture 48. The fiow of air along the axis of the cone 56 is blocked at this point by a semicircular baffle 72 spaced somewhat from the duct 62 toward the center of the combustion chamber 12 and extending vertically from the lower portion of the cone 56 to a horizontal upper edge slightly above the duct outlet opening 64.

This structure sets up a high velocity vortex of burning fuel and air mixture which swirls around the air supply duct 62 to provide a high degree of preheating of the incoming air, which further improves volatilization and mixing of the fuel with the air. The swirling fuel and air mixture spills out of the burner cone 56 into the combustion chamber 12 as a high velocity vortex which continues the thorough mixing and burning of the fuel.

Additional or secondary air is supplied to the combustion chamber 12 through a cylindrical tube 74 substantially coaxial with the burner cone 56. The outer end of the tube 74 embraces a circular support boss 76 swaged inwardly from the header 26, Figs. 3 and 5. Air under pressure in the conduit 42 flows through a central opening 78 in the boss 76 into the tube 74 and through the tube to a series of outlet apertures 80 in a conical tip 82 on the tube, which extends somewhat beyond the vertical baffle 72 toward the center of the combustion chamber 12.

The effective diameter of the swirling vortex of burning fuel mixture is reduced somewhat by the restricted inner end of the burner cone 56 as it passes by the conical secondary air supply cone 82. Consequently, the streams of secondary air issuing from the apertures 80 are immediately caught in the swirling combustion gases. Although heated considerably in passing through the supply tube 74, the secondary air introduced into the center of the swirling vortex of burning air and fuel is somewhat cooler and therefore heavier than the burning fuel mixture. Hence, as the secondary air picks up circular velocity it tends to move to the outer periphery of the vortex to be evenly distributed throughout by a sheet metal baflie 84 attached to the exterior surface of the inner end of the burner cone 56 opposite the passageway 32. semicircular in transverse section, the baffle 84 extends longitudinally through the major portion of the length of the combustion chamber 12 in radially spaced relation to the inner end of the passage 32 and to adjacent portions of the envelope 14 on opposite sides of the passageway. A projection 86 centrally located on the free end of the baffie 84 is turned radially inward.

Thus, despite the high circular velocity of the fuel mixture in the combustion chamber 12, the hot gases are evenly distributed through the passageway 32 to the annular passages 34 by the pressure gradients created within the heat exchanger 10.

The structure of the more eflicient heater thus formed is well suited for economical fabrication largely from sheet metal.

While I have shown and described a preferred embodiment of my invention, it will be apparent that numerous variations and modifications thereof may be made without departing from the underlying principles and scope of the invention. I therefore desire, by the following claims, to include all such variations and modifications by which substantially the results of the invention may be obtained through the use of substantially the same or equivalent means.

I claim:

1. A high capacity combustion air heater comprising, in combination, heat exchanger means defining a generally cylindrical horizontally elongated combustion chamber having an outlet opening extending longitudinally along one side thereof and a header at one end thereof, said heat exchanger means defining a combustion gas passageway communicating with the combustion chamber outlet opening and defining a passageway for air to be heated, an inwardly open burner cone extending into said combustion chamber from said header, the inner end of said cone being sharply necked inwardly, an arcuate duct attached to the inner face of said header in radially spaced substantially coaxial relation to the inner surface of said burner shell, said header defining an air inlet opening extending into one end of said duct, the opposite end of said duct opening downwardly toward the underlying portion of said burner shell, an upwardly extending bafile on the lower portion of said shell located forwardly of said duct outlet, means for supplying fuel into the lower portion of said burner shell between said header and said bafile, said header defining a second air inlet opening therethrough near the center of curvature of said duct, a tube on the inner face of said header communicating at one end with said second air inlet opening and extending forwardly substantially to the necked down end of said burner cone, the end of said tube opposite said header defining outlet openings for distributing secondary air to a vortex of a fuel air mixture formed by air admitted through said duct.

2. A high capacity combustion heater comprising, in combination, heat exchanger means defining a generally cylindrical horizontally disposed combustion chamber having an outlet opening along one side thereof and a header at one end thereof, said heat exchanger means defining a hot combustion gas passage communicating with said combustion chamber outlet opening, said heat exchanger means defining a passage for air to be heated, an annular burner shell opening into said combustion chamber from the inner face of said header, a semicircular duct attached to the inner face of said header and substantially coaxial therewith, said header defining a first air inlet communicating with one end of said duct, the opposite end of said duct opening downwardly into the underlying portion of said burner shell, a generally vertical bafiie in the lower portion of said burner shell, means for supplying fuel into said burner shell between said header and said bafiie, the medial portion of said header defining a second air inlet therethrough, a tube connected with said second air inlet and extending beyond said duct toward the medial portion of said combustion chamber, the end of said tube remote from said header defining at least one air discharge opening for 5 comingling secondary air with fuel in a vortex of air admitted through said duct, and a transversely curved baffle attached to said burner shell and extending longitudinally through the major portion of said combustion chamber in spaced covering relation to said outlet open- 10 ing therefrom.

References Cited in the file of this patent UNITED STATES PATENTS Heuermann June 25,

Clymer May 15,

McCollum June 26,

Allen et al. May 9,

Hillery et al. Dec. 6,

FOREIGN PATENTS Great Britain Jan. 14, 

